[time-nuts] Spacecraft Timekeeping

[Chris Albertson]

On Tue, Mar 8, 2011 at 11:05 PM, Magnus Danielson
<magnus at rubidium.dyndns.org> wrote:


I'm still wondering exactly which spacecraft this person is working
on.  His questions are not indicative of current leading edge research
in this area.  Sounds like he is starting from zero and maybe not up
to speed on current best practice.   Use of GPS in space is now, I
think a mature technology and there are several space-qualified
receivers.

There are simple little things that may prevent you from using off the
shelf commercial receivers (1) vacuum is a very good insulator,
thermal design is different if you have air vs. vacuum (2) Power and
weight.  (3) materials, (4) EMI,  ....(100)   Not that it can't be
done but there are 100 things you'd need to know and checkout and you
need to buy a statistically valid number of these units and test them
in simulated conditions.  It's an expensive process that has risk to
schedule and budget because you can't predict the outcome of the
qualification process in advance.   Hence the small industry of
companies selling pre-qualified units.   That said, If this is an
amateur sat. project or a university funded project them it's worth it
because you have nearly unlimited free labor for engineering and QA.

-- 
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Chris Albertson
Redondo Beach, California